Language fluency

Fluency (also called volubility and eloquency) is the property of a person or of a system that delivers information quickly and with expertise.

Fluency is a speech language pathology term that means the smoothness or flow with which sounds, syllables, words and phrases are joined together when speaking quickly. "Fluency disorders" is used as a collective term for cluttering and stuttering. Both disorders have breaks in the fluidity of speech, and both have the fluency breakdown of repetition of parts of speech. Fluency disorders are most often complex in nature and they tend to occur more often in boys than in girls.

Language fluency is the degree to which one is fluent in a language. Someone is said to be fluent if they have a high level of language proficiency, most typically in a foreign language or another learned language, and more narrowly to denote fluid language use, as opposed to slow, halting use. In this narrow sense, fluency is necessary but not sufficient for language proficiency: fluent language users (particularly uneducated native speakers) may have narrow vocabularies, limited discourse strategies, and inaccurate word use. They may be illiterate, as well. Native speakers are often incorrectly referred to as fluent.

Fluency is basically one’s ability to be understood by both native and non-native listeners. A higher level would be bilingual, which indicates one is capable of speaking in two languages, either having learned them simultaneously or one after the other.

In the sense of proficiency, "fluency" encompasses a number of related but separable skills:

To some extent, these skills can be acquired separately. Generally, the later in life a learner approaches the study of a foreign language, the harder it is to acquire receptive (auditory) comprehension and fluent production (speaking) skills; however, the Critical Period Hypothesis is a hotly debated topic. For instance, reading and writing skills in a foreign language can be acquired more easily after the primary language acquisition period of youth is over.

...
Wikipedia